1. Field of the Invention
One embodiment of the present invention relates to a semiconductor device, a display device, or an electronic device. Further, one embodiment of the present invention relates to, for example, a circuit, a processing circuit, or a memory circuit, which utilizes a semiconductor, a driving method thereof, a manufacturing method thereof, or the like.
2. Description of the Related Art
For pixels of an active matrix display device using light-emitting elements, a variety of circuit configurations have been proposed. In general, at least a light-emitting element, a transistor that controls input of a video signal to a pixel, and a transistor (driving transistor) that controls current supplied to the light-emitting element are provided in the pixel. Supplying a drain current flowing through the driving transistor to the light-emitting element enables the light-emitting element to emit light with a luminance corresponding to the value of the drain current. The drain current of the driving transistor is controlled by voltage of a video signal.
Therefore, in the case where electrical characteristics (e.g., threshold voltage, field-effect mobility) of the driving transistor vary among a plurality of pixels that constitute a screen of a display device, variations in luminance of the light-emitting element are generated even when video signals with the same voltage are supplied. Variations in electrical characteristics of the driving transistor among a plurality of pixels are one of the causes of reduction in display quality of a display device.
For active matrix display devices, the number of pixels to be provided has been increased to achieve higher resolution, and hundreds of thousands to tens of millions of pixels are provided in one display device. For example, the number of pixels is 1,049,088 (1,366×768×3 (RGB)) for the resolution of Full-HD, and is 33,177,600 (7,680×4,320×3 (RGB)) for the resolution of 8k4k (super high-vision). It is very difficult for driving transistors of a large number of different pixels to have perfectly the same electrical characteristics. Thus, measuring the electrical characteristics of a driving transistor and correcting the luminance of a light-emitting element is proposed (Patent Document 1, for example).
In order to meet demands for a larger number of gray levels and higher resolution of a display portion or the like, a dedicated IC (driver IC) is used in a driver circuit of a display device, particularly in a source driver circuit (see Patent Document 2, for example).
In a pixel circuit or a driver circuit of a display device, a transistor including a semiconductor thin film (also referred to as a field-effect transistor (FET) or a thin film transistor (TFT)) is often used. In recent years, an oxide semiconductor has been attracting attention as a semiconductor thin film that can be used for such transistors (Patent Document 3).